african broad-mouthed collagen cow creases eating endangered flat-mouthed folds food gray grazer grey heavy herbivore herbivorous hide horns junior keratin large lattice-structured mammal megafauna mother odd-toed-ungulate offspring perissodactyl placid powerful rhino rhinoceros skin snout southern-white-rhinoceros square-lipped rhinoceros strong thick threatened tough white rhinoceros wide-lipped rhinoceros wrinkled wrinkles calf youngster armor armored armorment armour armoured armourment Australian-freshwater-crocodile backstraps basking bony ridges crocodile crocodilian crocodylus-johnsoni crocodylus-johnstoni danger dangerous dorsal-surface exotic fauna freshie hornback Johnston's-crocodile leather leathery lethargic omnivorous opportunistic opportunistic-predator osteoderms patterns predator reflection reptile reptilian ridges rough rugged scales scutes tail territorial texture textured textures close close-up eye eye-lashes eye-lid crocodylus-porosus estuarine-crocodile huge Indo-Pacific-crocodile largest-reptile saltwater-crocodile tail-scutes